Total prosthetic replacements of the human hip, knee and shoulder are now common orthopedic surgical procedures. As the age of the general population increases, the frequency for such replacements will increase. Symptoms generally include progressive degenerative osteoarthritis, prior localized trauma, previous local surgical procedures within the region, ankylosing spondylitis, and idiopathic skeletal hyperostosis.
A common delayed complication following such replacements is the development of heterotopic ossification within or about the immediate adjacent soft tissue and the prosthesis between the adjoining bone tissue. This complication results from excessive migration, replication, or differentiation of local primitive mesenchymal cells which are stimulated by the surgical trauma. These cells undergo subsequent metabolic and cytologic metamorphosis to become more specialized osteoblastic cells. These osteoblastic cells then produce osteoid which is eventually transformed into calcified deposits or bone tissue, but in undesirable locations.
Heterotopic ossification causes varying degrees of debilitating pain, functional or mobile impairment, and increases the likelihood of repeat procedures after a period of from several months to a few years. For all patients undergoing total prosthetic hip replacement, between 30 and 35 percent of all untreated patients develop some degree of functional impairment or progressive discomfort.
External beam irradiation has established therapeutic effectiveness. When such therapy is delivered within a narrow period of time, the prophylactic use of external beam radiation therapy has been shown to effectively reduce the incidence and severity of heterotopic ossification. A limited, relatively low-dose of focal ionizing radiation to the specific target tissue, when administered predominantly in the first several hours to two days after surgery has proven beneficial clinical results with virtually no short or long term side effects.
However, external beam radiation therapy is often not prescribed because of the time required for set-up and treatment, the availability of single fraction treatments and variations in prescribed dose, patient discomfort and side effects, the need to irradiate tissue outside the target field, and economic considerations. In addition, many patients are not considered for radiation treatment until late in the recovery process, which further limits treatment options.
What is needed is a process and structure for providing the radiation dose originating from an internal site to the targeted tissue, whereby the emission profile more closely matches the physical parameters profile of the targeted tissue than in conventional methods.
What is needed is a process and a structure that will eliminate the need for separate post-operative treatment while dramatically reducing any occurrence of heterotopic ossification.
What is needed is a process and a structure that is can be readily adapted for any surgical bone tissue replacement or additive procedures.
What is needed is a process and a structure that is easy to administer, safe for the patient, and will effectively reduce the formation of heterotopic ossification resulting from such surgical procedures.